Efficiency of industrial-scale radio frequency treatments to control Rhyzopertha dominica (Fabricius) in rough, brown, and milled rice

Abstract

Many disinfestation processes developed in pilot-scale radio frequency (RF) systems reveal that RF treatment is a promising non-chemical method to control insects in postharvest agricultural products. The purpose of this research was to determine efficiency of RF treatment for disinfesting rice in industrial applications. A free-running oscillator 27.12 MHz, 15 kW RF system was used to conduct the industrial-scale and continuous treatment, and estimate the corresponding throughput, heating efficiency and electrical cost for controlling adult lesser grain borer , Rhyzopertha dominica , in rough, brown, and milled rice. The maximum throughputs for this RF system were obtained by heating three, three, and two layers of rough, brown, and milled rice to 54 °C under electrode gaps of 195, 235, and 180 mm, with conveyor belt speeds set to 10.9, 10.3, and 12.4 m h −1 , respectively. The 100% mortality of adult R. dominica was obtained when the temperature of samples reached 54 °C with holding for 11 min. Quality of treated rice was not affected by the RF treatments since no significant difference ( P > 0.05) was observed in physical and nutritive quality attributes between control and RF treated rice except for moisture content for rough rice and water activity for brown rice. The average heating efficiency and throughput of the RF system for rough, brown, and milled rice were 59.9, 62.5, and 54.5%, and 313.6, 594.8, and 476.2 kg h −1 , resulting in the electrical costs of US$ 2.68, 2.53, and 3.13 per 1000 kg, respectively. This research demonstrated potential RF industrial applications for rice processors to adopt effective non-chemical disinfestation methods. • Industrial-scale RF treatments were developed for disinfesting rice. • Sample temperature of 54 °C for holding 11 min resulted in 100% mortality. • Quality of treated rice was not significantly affected by RF treatments. • Heating efficiency, throughput and electrical cost of RF systems were determined.